1. Field of the Invention
This invention relates to the treatment of psoriasis and, more particularly, to a method for treating psoriasis by topically applying isoniazid in a carrier base to the psoriasis lesion.
2. The Prior Art
Psoriasis is a common but complicated, proliferative and inflammatory disease of the skin. Psoriasis is usually chronic though sometimes acute and affects about two to three percent of the United States population. About 500,000 of these victims of this painfully disfiguring disease experience serious difficulties finding anything resembling a normal life. Additionally, a severe psoriatic arthritis may totally incapacitate the patient and make employment almost impossible. Extensive involvement of the skin, of the feet and hands may make weight-bearing intolerable and simple motions of the digits next to impossible. The large prominent red plaques on the skin and the continual sloughing of scales are a source of constant embarrassment because of misunderstanding or even ridicule on the part of those who behold the marred skin surface of the carrier. Accordingly, psoriasis is not just a skin disease; it is a highly personal tragedy.
Psoriasis is unusual in children but relatively common at any age after puberty. Genetic factors are presently considered to be of prime importance in transmission of the disease, but environmental agents appear to also play an important role. For example, certain psoriatic lesions unquestionably have been produced by some blunt mechanical trauma, possibly of a chronic nature. For example, the mechanical trauma can result from carrying a heavy suitcase, ironing, gripping a steering wheel or swinging of a golf club. On occasion, the mechanical trauma may be occupational in origin, such as in a seamstress or one working with heavy cardboard boxes. This latter sequence is well known as Koebner's phenomenon.
The early stage eruption of psoriasis may be non-specific in appearance. In fact, early psoriasis is often confused with a variety of skin diseases such as drug eruptions, dermatitis, fungus disease, insect bites and chicken pox. Early lesions are asymptomatic although some patients complain of mild pruritus. The initial lesion is an erythematous papule which may progress to pustulation, accounting for the confusion with chicken pox. Soon after the erythematous papules, the characteristic papulosquamous plaque appears. The typical psoriatic eruption consists of erythematous, scaling plaques of variable size. The lesions are, in most cases, symmetrical.
Clinically, the scale is distinctive, silvery and luxuriant in its pristine, untreated state. Underneath is a dull red surface which, upon removal of the scale, may show fine capillary bleeding points. Always sharply limited in border and frequently clearing in the center, psoriasis may come in any size and the scale, may, in turn, range from being absent to extremely thick.
Psoriasis, in addition to being an inflammatory disease, is a benign hyperplastic disease of the skin. Importantly, epidermal cells in areas of skin involvement have a very rapid rate of replication. The mitotic index of the germinative cell population per unit length of involved epidermis is increased, and there is a reduced epidermal cell transit time, or epidermal cell "turnover" time in involved areas. Accordingly, the epidermis of the psoriatic lesion grows very fast (about ten times normal rates) and sheds large amounts of scale. This is one of the key factors in the pathology of the disease.
In view of the foregoing, the principal thrust of the treatment protocol centers around use of antimetabolites or nicotinamide antagonists, such as the topical application of Methotrexate, and folic acid antagonist; Azaribine, an orotidylate decarboxylase inhibitor (triacetyl-6-azauridine); Hydroxyurea; 6-aminonicotinamide; and systemicly with mycophenolic acid. The first three drugs are antimetabolic agents and have been reported effective in producing remissions in patients with severe recalcitrant disease.
However, all of these drugs have major side effects and can be given only in very severe cases and under extremely careful supervision by those experienced in their use. In many instances, some of the adverse effects of these drugs are worse than the psoriasis particularly when using antineoplastic agents.
Other topical agents are generally quite safe, and with diligent, continuous application can be effective. The oldest and most widely used topical agent is crude coal tar in conjunction with exposure of the psoriatic lesion to ultraviolet light. Other topical agents which have been found useful are anthralin, topical glucocorticosteroids, ammoniated mercury, and vitamin A acid.
In view of the foregoing what is needed in a method for treating psoriasis by the topical application of a suitable compound to the psoriatic lesion. It would be an even still further advancement in the art to provide a known compound for which extension physiological studies have been made and use the same in the method for treating psoriasis. Such a discovery is disclosed herein.